Large area floating structures are useful for providing enlarged areas for a number of large scale operations, such as: offshore petroleum drilling, production and storage; liquefied natural gas on-loading and storage, re-gasification, pressurization and off-loading; electric power plants, both hydrocarbon and nuclear fueled; de-salination water plants; airports, seaports, military bases, living accommodations, floating piers, breakwaters, harbors and the like.
Such structures are most economically fabricated in pre-stressed, steel reinforced concrete composites. Such large area structures are typically tightly coupled by buoyancy to the water surface, and waves can impart undesirable motions and induce undesirable dynamic and static stresses in the structures. Because concrete structures are susceptible to failure when stressed in certain ways, these structures stresses must be mitigated. To adequately mitigate these stresses, ways to enhance de-coupling of the floating structures from the buoyant excitation by sea waves must be employed.
Floating structures for large-scale operations may be similar to those described in U.S. Pat. No. 5,375,550. These platforms may include a closely packed array of vertical concrete cylinders, each of which includes an open bottom and a capped top that combine to form a working platform. The air trapped in the cylinders, when pressurized, displaces water from the cylinders providing buoyancy for the platform. Air in the cylinders may also be in air or gaseous communication with adjacent cylinders via orifice passages/ducts. The compressibility of the air and its ability to move from one cylinder to an adjacent cylinder helps to desensitize or decouple the platform from buoyant wave excitations.